Kinetic and Dynamic Models of Diving Gases in Decompression Sickness Prevention Robert Ball 1 and Sorell L. Schwartz 2 1 Decompression Program, Diving and Environmental Physiology Department, Naval Medical Research Institute, Bethesda, Maryland, USA 1 2 Department of Pharmacology, Georgetown University Medical Center, Washington DC, and International Center for Toxicology and Medicine, Rockville, Maryland, USA Abstract Decompression sickness is a complex phenomenon involving gas exchange, bubble dynamics and tissue response. Relatively simple deterministic compart- mental models using empirically derived parameters have been the mainstay of the practice for preventing decompression sickness since the early 1900s. De- cades of research have improved our understanding of decompression physiol- ogy, and the insights incorporated in decompression models have allowed people to dive deeper into the ocean. However, these efforts have not yet, and are unlikely in the near future, to result in a ‘universal’ deterministic model that can predict when decompression sickness will occur. Divers using current recreational dive computers need to be aware of their limitations. Probabilistic models based on the estimation of parameters using modern statistical methods from large databases of dives offer a new approach and can provide a means of stand- ardisation of deterministic models. Future improvements in decompression prac- tice will depend on continued improvement in understanding the kinetics and dynamics of gas exchange, bubble evolution and tissue response, and the incor- poration of this knowledge in risk models whose parameters can be estimated from large databases of human and animal data. LEADING ARTICLE Clin Pharmacokinet 2002; 41 (6): 389-402 0312-5963/02/0006-0389/$25.00/0 © Adis International Limited. All rights reserved. Decompression sickness (DCS) can affect scuba and surface-supplied divers, caisson work- ers, aviators and astronauts after a change from a higher to a lower ambient pressure. Symptoms and signs can include painful joints, neurological dys- function, skin rash and, in some cases, cardiopul- monary collapse. [1] The putative cause of DCS is tissue injury resulting either directly or indirectly from the formation of bubbles of inert gas (e.g. nitrogen in air diving) during decompression caused by super-saturation of tissue with inert gas. [2] The primary factor influencing DCS risk is the dive pressure profile; environmental conditions and individual physiological factors play a smaller role. [2,3] The risk of DCS among divers in field settings is not well defined because it is difficult to system- atically collect data on the number of DCS cases, the number of dives and the precise depth-time pro- files for these dives that is necessary to make this 1 Dr Ball was affiliated to the Naval Medical Research Unit between 1995 and 1997.